The present invention relates generally to semiconductor sensor devices and, more particularly to a cavity type pressure sensor device and a method of assembling same.
Semiconductor sensor devices, such as pressure sensors, are well known. Such devices use semiconductor pressure sensor dies. These dies are susceptible to mechanical damage during packaging and environmental damage when in use, and thus they must be carefully packaged. Further, pressure sensor dies, such as piezo resistive transducers (PRTs) and parameterized layout cells (P-cells), do not allow full encapsulation because that would impede their functionality.
Typical cavity style pressure sensing devices are assembled by placing a pressure sensing die in a pre-molded enclosure on a lead frame. The die is electrically connected to device leads (and/or other devices) with bond wires. A cavity is formed over the die by the enclosure, and the cavity is filled with silicone gel to protect the die. However, micro-gaps can be present at interfaces between the plastic molding material and the lead frame. Further, when the sensor device is exposed to high pressure and decompression, air bubbles can be formed inside the gel, which can interact with the bond wire interconnections and the MEMS structure of the die, causing device read errors.
Since the size of the pre-molded package cavity is typically large and the gel used to fill the cavity is expensive, it would be advantageous to be able to reduce the volume of gel material used to fill the cavity. It also would be advantageous to reduce the opportunity for bubble formation.